A hybrid vehicle may transition from a driveline regeneration mode to a driveline acceleration mode. During the driveline regeneration mode, an electric machine in the driveline provides a negative torque to the driveline and converts the vehicle's kinetic energy into electrical energy. During the acceleration mode, the electric machine and/or an engine provide positive torque to the driveline to accelerate the vehicle. Thus, the driveline may transition from providing a negative torque to vehicle wheels to providing a positive torque to vehicle wheels, or vise-versa. During a change in the driveline torque sign, lash between gears in the driveline may provide an audible noise as well as a momentary lapse in driveline torque. The lapse in torque and audible noise may be objectionable to a driver.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for operating a driveline, comprising: stopping rotation of an engine and providing regenerative braking via a driveline; transitioning from the regenerative braking to providing positive torque to the driveline; and operating a driveline integrated starter/generator in a speed control mode during the transition.
By operating a driveline integrated starter/generator in a speed control mode during a transition from regenerative braking to a positive driveline torque, gear tooth to gear tooth impact may be reduced. Further, since torque delivered through a torque converter in a driveline is dependent on torque converter impeller speed and torque converter turbine speed, and since the driveline integrated starter/generator is coupled to the torque converter impeller, the driveline integrated starter/generator speed may be adjusted to reduce the possibility of a lapse in driveline torque during the transition.
The present description may provide several advantages. In particular, the approach may reduce driveline torque disturbances of a hybrid driveline. Further, the approach may improve vehicle drivability. Further still, the approach may reduce driveline wear, thereby increasing the operating life of the driveline.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.